Thermal equilibrium conditions (majority carriers * minority carrier concentration = square of carrier concentration); electrical neutrality conditions (majority carriers = doped minority carriers)

The majority carrier concentration is approximately equal to the dopant concentration and has nothing to do with temperature; the minority carrier concentration increases significantly as the temperature increases.

When the temperature rises, impurity semiconductors turn into intrinsic semiconductors

Diffusion movement (concentration difference)

Drift motion (electric field force)

Concentration difference, multi-carrier diffusion, generation of space charge region, built-in electric field (hinders multi-carrier diffusion and facilitates minority carrier drift), dynamic balance

Forward voltage, the direction of the external electric field is opposite to the internal electric field, the depletion layer becomes narrower, the diffusion movement intensifies (the polyon concentration increases), and the conductivity increases

Forward conducting, reverse blocking

reverse breakdown

Barrier Capacitance (Varactor Diode)

Diffusion capacitance

ideal model

Constant voltage (drop) model

polyline model

At the static operating point, the diode is equivalent to a dynamic resistance (AC resistance), rd = UT/ID. The higher the Q point, the smaller rd

Volt-ampere characteristics (breakdown area is very shaking)

Main parameter

Solve problems

Using PN junction to be sensitive to light

Forward bias conduction characteristics (LED lights, display screens)

Barrier Capacitance Characteristics

Three configurations

Current amplification coefficient: common emission b, common base a

Two equations (IE=IB IC,IC»bIB)

Cutoff area, saturation area, amplification area

As the temperature increases, the UBE(on) turn-on voltage decreases, the reverse saturation current of the ICBO collector junction increases, and b increases

magnification mode

saturation mode

cutoff mode

h parameter equivalent model (mixed Π type small signal model), rbe=rbb` (given in the question stem) bUT/ICQ